Project 2: Sex Differences in Health and Survival in the Danish Population Disabilities are strong predictors of mortality at older ages. Males are less physically disabled than age- matched females and still they have substantially higher mortality. The current project aims to shed light on the basis for the difference in the health-survival association between males and females through the use of unique data resources in Denmark consisting of large longitudinal surveys of twins and the entire Danish 1905-cohort. Because health related selective non-response is a major bias in studies of the elderly, this project will be supplemented with a linkage to Statistics Denmark's nationwide registers including information on socio-economic status as well as on medication, hospitalization and death for all individuals in the cohorts under study - including thenon-responders. These extensive data sets will initially be used to assess to what extent the health-survival paradox is due to the definition of health and how health is measured. Our main hypotheses are that the health-survival paradox is partly due to different transition rates from an unhealthy state to either death or a healthy state for males and females and that it is more the rate-of-change than the level of functioning that is predictive of survival among the elderly and the oldest-old. The dataset also enables us to test whether males with health problems are less likely to participate in surveys than females with similar health problems and whether there is more reluctance among males to seek medical treatment. The international scope of this P01 enables us to assess to what extent the observed sex differences are constant across populations in Denmark, USA, and Asia. RELEVANCE (See instructions): Is it true that males are healthier than females but die younger? If so, why? This research project addresses these questions concerning the human health-survival paradox. Findings will provide a deeper understanding of the basis for sex differences in health and survival and of the opportunities society and particularly health professionals have to improve health and survival for both males and females.